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From: "fsb4000 at yandex dot ru" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug libstdc++/106607] New: Regex integer overflow on large
 backreference value
Date: Sat, 13 Aug 2022 09:26:27 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106607

            Bug ID: 106607
           Summary: Regex integer overflow on large backreference value
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fsb4000 at yandex dot ru
  Target Milestone: ---

Hello!
I was fixing some MS STL issues with regex: GH-2168: integer overflow on la=
rge
backreference value and I added a test.
After that I decided to try my test with LLVM libc++ and GNU libstdc++.
LLVM libc++ passes my test.
and libstdc++ doesn't pass it.

```
#include <cassert>
#include <regex>

using namespace std;

// GH-2168 <regex>: integer overflow on large backreference value
int main() {
    try {
        // 4294967297 =3D 1 mod 2^32, so this will succeed if we don't chec=
k for
overflow.
        regex testRegex{R"((a)\4294967297)", regex_constants::ECMAScript};
        assert(false);
    } catch (const regex_error& e) {
        assert(e.code() =3D=3D regex_constants::error_backref);
    }
}
```

https://gcc.godbolt.org/z/nzET6nvxo=